1. Field of the Invention
This invention relates to a semiconductor photoelectric transducer, and more particularly, to a semiconductor photoelectric transducer having a spectral sensitivity selectively in the visible light wavelength region.
2. Description of the Prior Art
Heretofore, semiconductor photoelectric transducers having a spectral sensitivity selectively in the visible light wavelength region have been prepared by various methods as shown below. For example, cadmium sulfide is doped with an acceptor impurity composed of a metal element of Group I of the Periodic Table such as copper and the like by using cadmium chloride as a flux to impart selectively a spectral sensitivity at the visible light wavelength region. In the case of zinc oxide, an organic colorant is adsorbed to zinc oxide to impart selectively a spectral sensitivity corresponding to the light absorption of the adsorbed colorant.
In addition, it is also well known that silver halides are sensitized with cyanine dyes and xanthene dyes so as to impart a spectral sensitivity at the long wave length region.
As a material for semiconductor photoelectric transducers, there may be mentioned Group II-VI compounds such as CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe and the like, Group III-V compounds such as GaP, InSb and the like, of Group IV such as Ge, Si and the like, and organic photo-conductive materials. Among them, Group II-VI compounds are preferable. Silicon has been recently used in a great amount because silicon resources are very rich.
It has been heretofore known that photoconductivity is often observed when organic colorants are selectively irradiated with a visible light. However, such conventional organic colorants generally have a low sensitivity and the time required for rise and decay (response time) of photocurrent is as long as from several minutes to several tens minutes and therefore, it is difficult to use conventional organic colorants as a practical photoelectric transducer.